This project seeks to isolate, purify, and characterize human mucosal mast cells from the colon, and to investigate how such cells are involved in the regulation of gastrointestinal physiology and pathophysiology. Human mucosal mast cells will be obtained from surgical specimens of human colon by enzymic dispersion, purified by centrigual elutriation, density gradients and/or negative selection techniques, and characterized according to the types and amounts of mediators they produce, and their responsiveness to degranulating and inhibitory agents. Attempts will also be made to grow; or maintain the cells in tissue culture either by establishing co-cultures between the mast cells and fibroblasts from various sources, or by using as potential sources of mast cell growth factors such agents as preparations from mitogen-stimulated human lymphocytes, or gibbon or murine IL-3. Having identified the types and amounts of mediators synthesized by mucosal mast cells, the ability of these mediators to cause colonic salt and water secretion will be tested using a model epithelium, the T84 cell line, and Using chamber methodology. The possibility that T84 cells can produce mediators capable of modulating mast cells function will also be investigated. Finally, mast cells will be obtained from intestinal tissue specimens of patients with inflammatory bowel disease, or other immune- related gastrointestinal diseases as available. The properties of such cells will be examined, and compared with those of normal mucosal mast cells in terms of mediator content, mechanisms of activation and inactivation, and control of growth and differentiation. In toto, the project should increase knowledge of the properties of human mast cells in health and disease. It is hoped that definitive information will be derived as to whether mucosa mast cells play a role in he regulation of intestinal physiology, such as the control of electrolyte transport, and/or the generation of intestinal pathology, such as in inflammatory bowel disease. A role for mast cell activation has been postulated in the generation of inflammatory bowel disease, and other immune-related gastrointestinal disorders, but has not been conclusively demonstrated. Inflammatory bowel disease represents a significant, and increasing, cause of morbidity and mortality, especially in developed countries. This study may shed more light n these conditions, and thus suggest new therapeutic modalities.